Hi epanska
It really isn't a silly question at all.
Copy slide and Duplicate slide essentially do the same thing.
Here's the main difference.
If you use Copy slide, the slide contents are simply captured
and placed in the Windows clipboard, ready to be pasted elsewhere.
On the other hand, Duplicate slide makes a copy of the
existing slide and presents it to you. This saves you from having
to paste the slide elsewhere.
Hopefully this was helpful to you... Rick